Telegraphy



J. H. BELL.

TELEGRAPHY.

APPLICATION FILED Aus.14. 1918.

1,336, 11 4. Patented Apr. 13, 1920.

2 SHEETS-SHEET 1.

ply

J. H. BELL.

TELEGRAPHY.

APPLICATION} FILED AUG. 14. 1918.

Patented Apr. 13, 1920.

2 SHEET3-SHEEF 2.

W My ITED STATES PATENT ormon.

JOHN H. BEQIIIII, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR T0 WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK.

TELEGRiAlI-IY.

1,336AML.

Specification of Letters Patent.

Patented Apr. 13, 1920.

Application filed August 14-, 1918. Serial No. 249,812.

To all whom it may concern:

Be it known that I, JOHN H. BELL, a citizen of the United States,residing at South Orange, in the county of Essex, State of New Jersey,have invented certain new and useful Improvements in Telegraphy, ofwhich the following is a full, clear, concise, and exact description.

This invention relates to telegraph systems and more particularly tocable or submarine telegraphy.

The principal object ofthis invention is to provide an improvedorganization of apparatus-to prevent so-called wandering-zero effects intelegraph conductors having high electrostatic capacity characteristics.

In carrying out the present invention there is provided, in addition tothe usual tape controlled transmitting contacts and currentdistributors, an arrangement of circuit controlling devices, whereby thepotential or current strength of successive impulses may beautomatically varied in accordance with a predetermined relation as tothe electrical condition of a cable or line ponductor.

This invention is illustrated diagramlnatically in the accompanyingdrawing, in which, for the sake of clearness, only such portions of atelegraphic equipment have been shown as will be necessary to a clearunderstanding of the features of the system.

In Figure 1 of the drawing is shown a transmitting equipment which maycorrespond with one arm or section of a'multiplex equipment and is arraned for use in connection with one channe of a multiplexed line. In Fig.2 there is shown an equipment for transmission over a second channel ofthe same line conductor and this equipment differs from the equipmentshown in the first figure only in that devices common to the cable orline conductor are also included in this figure.

In order that this invention may be more readily understood, the servicefeatures of the system will first be briefly described. Accordingly, inthe operation of printing telegraphs it is well understood that whengroups of character selecting impulses are impressed on a cableconductor, as in following an interval during which successive impulsesof like polarity may have occurred, the electrical condition of thecable will become asymmetrical with respectto the true zero potentialcondition thereof, and therefore, succeeding impulses of oppositepolarity may not build up to a strength sufiicient to neutralize orproperly overcome such electrically distorted condition of the lineconductor. The present invention therefore contemplates that in additionto providing that the cable may be grounded during impulse intervalswhich may correspond with successive repetitions of like currentpolarities, a system for controlling many different current potentialsmay be so arranged that following a period during which the cable mayhave been grounded, the value of a next succeeding impulse may be ofsuch modified strength as to prevent an undue building-up and chargingefiect in the cable. As carried out, this potential varying'systemprovides that for successive impulses of inverse polarities the strengthof the currents may be the same. After the cable has been groundedduring a single impulse interval, however, a single fold reduction ofpotential may become effective with the nextsucceeding impulse ofopposite polarity, and when an impulse follows two impulse intervalsduring which the cable may have been grounded, current having a two-foldreduction in potential will form such impulse. In a corresponding mannera third, fourth, fifth, or more, reduction of the line currentpotentials may be effected after third, fourth, fifth, or moreconsecutive impulse intervals, respectively, during-which the cable mayhave continued grounded. By means of a proper gradation of the variouspotential values, the electrical condition of a cable conductor may thusbe maintained at a practically true electrical zero.

In more specifically describing this system it will be noted that theequipment of the first multiplex channel, shown in Fig. 1, comprisesautomatic contact levers 15 which will be understood as arranged in amanner adapted for control by a suitably notated or perforatedtransmitting tape. In turn, these contacts control the operation of polechanger relays 1115 which determine the polarity of currents employed insignaling. Relays 21-25 connected to be controlled through respectivelyadjacent ones of the transmitting contact levers 15 serve for normallygrounding a cable L (Fig. 2) and for connecting this cable to receivecurrent as selected by the pole changer relays 11-15. In addition toselectively connect ing either ground or current to the cable, the

grounding relays 21-25 also serve with current potential control relays31-35 in rendering resistance units 146-150 effective to suitably varythe potential of the line currents which may have been selected, theseresistances being further under control of a master relay 140, connectedto form a series common to the operating circuit of each relaycomprising the group 31-35. In applying the resistances to vary thepotential of the impulses, current protective or limiting resistancesare included in the leads through which current is supplied to thecable, and the current modifying resistances are, at proper moments,connected to serve in parallel or bridge from the cable. conductor toearth,-thereby constituting a path or paths in parallel with the cablefor deflecting a portion of the line current therefrom. Since in theBaudot code which, for

convenience of description, has been selected as the transmission basisof the present system, each character selecting group is formed ofpermutations of five successive impulses of opposite polarities, thereference characters A, C, D and E have been employed and positioned torespectively correspond with successive ones of five impulse intervals.The equipment positioned directly below these reference characters andset off by the vertical guide lines correspond with the devicesassociated with the respective impulseperiods. Accordingly, for thefirst impulse in this quadrant or section of the multiplex equipment,the transmitting contact 1, relays 11, 21 and 31, and distrib-- utersegments 41, 51, 61, 71 and 81 correspond with this first impulseinterval of a character selecting series, while transmitter contact 2,relays 12, 22 and 32, and distributer segments 42, 52, 62, 72 and 82correspond with a second impulse interval, this order continuing asindicated by the reference characters C, D and E for the last threeimpulse periodsfof a series.

The equipment shown in 2 of the drawing corresponds with a secondchannel of the duplex equipment, and the arrangement of the localdevices is the same as the arrangement alread. described in connectionwith the first gure. Briefly enumerated, this equipment comprisestransmitting contacts 6-10, pole changer relays 16-20, grounding'relays26-30, potential control relays 36-40, master relay 160 and potentialvarying resistances 166-170 partially controlled by this relay.Therreference-characters F, G, H, I and J serve respectively todesignate the equipment directly associated with impulse intervalscorresponding with five character selectin impulse periods for thissecond channel. In this figure of the drawing a first polar relay 112 isarranged to respond to prepared line currents .and'operates in polarityunison with such currents. This relay servesas a holding or lockingrelay for retaining energized any one ofthe potential control relays31-40 which may have been operated in either one of the two distributersections. A second polar relay 116 is connected to be controlled bycurrents applied to the cable L, its connective relation being such thatthe movement of its armature will always be in opposite phase withrespect to the polarity of the operating impulses and the relation ofthe connections from oppositely poled lines batteries 104 and 108 asestablished with its contact stops. In serving as a common link to joinresistances 146-150 and 166-170 to the line batteries,

the relay 116 therefore connects these resistances to the battery havingpotential opposite to the line battery from which the relay may havelast received its operating current. I

Before proceeding with a more detailed tracing of circuits briefreference will be made to the distributer equipment. Although shownindeveloped form, this distributer may be of a suitable rotary type inwhich brushes 126 and 127 may traverse their respective paths from leftto ri ht over the segments-of the two channels (Big. 1 and Fig. 2). Thebrush 126, on arriving in the zoneA, serves to join the se cuts 41, 51and 61, while in zone B it joms the segments 42, 52 and 62, andrespectively joins corresponding segments as it passes through thesuccessive zones C-J. Abreast of the brush 126, the brush 1-27 while inthe zone A joins the segments 71 and 81, in zone B it joins the segments72 and 82 and in like manner respectively joins the correspondingsegments as it passes through the zones C-J. The segments 41-50 areconnected to control the operation of respective adjacent ones of therelays 31-40, while the segments 51-60 are connected in derived circuitrelation from the respective line circuit supply leads controlled by therelays 21-30, the segments 61-70 being connected to control theoperation of the first polar relay 112. It will be noted that segments71-80 .as connected to the segments 51-60 respectively, are in anadvance relation relative to the latter segments. Thus segment 71 inzone A connects to seg ment 52 in zone B,"segment 72 in zone B connectsto segment 53 in zone 0, this relation continuing respectively throughthe various zones and is completed where the segment 80 in the last zoneJ connects to the segment 51 in the first zone A. As may be noted, thesegments 81-90 are connected directly to the line or cable L.

In a more specific description of this system, a transmissioncombination willbe asimpulse combination represented by impulses ofalternately opposite polarity, be-

ginning with a first impulse of negative polarity, will be prepared onthe transmitter contacts in the first channel (Fig. 1), while an impulsecombination comprising first, second and third impulses of positivepolarity followed by a fourth negative impulse and a fifth impulse ofpositive polarity will be set up in the second channel (Fig. 2).Assuming for convenience of description that the impulse combinationsfor both channels are set up at the same time, this will result intransmitting contact levers 1, 3, 5, 6, 7, 8 and 10 continuing inthepositions in which they are shown in the drawing, while the contactlevers 2, 4'and 9 will be moved and held in their opposite or alreadytraced for the first impulse. The

right-hand positions. This results in the operation of pole changerrelays 12, 14 and 19, also in the operation of the grounding relays 21,22, 23, 24, 25, 26, 29 and 30. The operating circuit for the relay 12may be traced from the positive pole of a battery 101 by way of busconductor 103, thence through the winding of the relay 12 to a busconductor 102, which connects to the negative side of this battery.Relay 14 is similarly operated by being connected through the contactlever 4 across the battery 101, While the relay 19 is alsoestablishedacross the battery -101 by means of its associatedtransmitting lever 9. At the grounding relays an energizing circuit forthe relay 21 extends from the ne ative bus 102 through the winding of tis relay, thence byway of a conductor120 and the transmitter lever 10 tothe positive bus 103. In a corresponding manner 'the'relays 22, 26 and29 are operated through closure of respectively typical circuits presentdue to the adjacent transmitter levers now standing connected to theopposite bus conductors of the local battery 101. Since therelay 21stands operated while the relay 11 continues in its normal position, acircuit may be traced from the negatively poled and grounded linebattery 104 over a resistance 105 and bus conductor 106, thence by Wayof the normal contacts of the relay 11 and the forward contacts of therelay 21 to negatively energize thesegment 71 in the zone A and thesegment 52 in the zone B. The three resistance units shown common toeach of the transmitter contacts 110 are merely for the purpose ofregulating the quantity of current through the respective circuitscontrolled by these levers.

Before tracing circuits prepared by the other relays, etc., let it beassumed that the brushes 126 and 127 now arrive in the 'zone A.Accordingly, current from the negatively charged segment 71 may traversethe brush 127 to'the segment 81, thence serially through the segments82-85, conductor 135, and serially over segment 8690 to the cableconductor L-to flow outwardly thereover and also to operate the relay116 to close its con- .tacts 118. Disregarding for the moment the matterof the brush 126 being in the zone A and the described operation of therelay 116, the circuit of the second impulse may be traced from apositively poled and grounded battery 107 byway of a resistance .108,bus conductor 109, thence over the forward contacts of the relay 12 andforward contacts of the relay 22 to the segment 72 in zone B and thesegment 53 in zone C. On arriving in the zone B, the brush 127 joins thepositively charged segment 72 to the segment 82 and thereby causespositive energization of the cable Land opposite biasing of the relay116 to close its contacts 117, over circuits relay 112 and an associatedresistance to earth. This polar relay will then assume its negative biasto establish its contacts 114. The brush 126 also causes energization ofthe segment 42 which is connected through the winding of the relay 31, abus conductor 124, thence in parallel through the windings of the twomaster relays 140 and 160. The relays 31, 140 and 160 now operatedreceive locking current over a circuit which may be traced from anegatively poled and grounded battery 110, the contacts 114 of the polarrelay 112, a bus conductor 115, and the right-hand forward contacts ofthe relay 31. At this time the operation of the relays 31, 140, 160andl16 is idle with respect to circuits prepared through the associatedresistances 146150 and 166-170, due to the fact that the successiveimpulses in the first channel are of opposite polarities andaccordingly, the circuits of these resistances stand open at the normalcontacts of the relays 21-26 and 29 and 30. Therefore, attention may bedirected at once to the tracing of the last three impulses of theselecting operations for this channel, and although the circuits will berespectively traced for the operation of the relays 3235, theiroperation will, for the reason stated in connection with relays 31, 140,160 and 116 be idle or non-efl'ective during the transmission of theseimpulses. For the third impulse current from the negative bus conductor106 may traverse the normal contacts of the relay 13, the forwardcontacts of the relay 23 to energize the segments 73 and 54, therefore,when the brush 127 arrives in the zone C, the cable conductor L willreceive a negative impulse of, current, while the brush 126 willestablish the positively charged segment 53 with the segment 63 topositively bias the relay 112 to close its contacts 113. In addition tothe operation of this relay the brush 126 joins the segment 53 to thesegment 43, thereby energizing the relay 32 and the relays 140 and 160with current of positive polarity, following which these relays will beretained locked by current from a positively poled and grounded'source111 which may now traverse the contacts 113 of the relay 112, the busconductor 115, and the locking or right-hand forward contacts of therelay 32. It will be pointed out that at the instant the relay 112 waslast operated to separate its contacts 114,,the negative battery 110 wasdisconnected from the bus con .ductor 115, thereby permitting therelease of the relay 31 and the relays 140 and 160. For

25 the fourth impulse, positive current from the bus conductor 109 maytraverse the forward contacts of the relays 14 and 24 to energize thesegments 74 and 55, therefore on arriving in the zone D, the brush 127impresses a positive impulse on the cable lead L, while the brush 126causes the lock control relay 112 to assume its negative bias toseparate its contacts 113 and to close itsv contacts 114. Separation ofthe contacts 113 disconnects the locking battery 111 to release therelays 32, 140 and 160 while the brush 126 also causes the initialoperation of the relay 33 and reoperation of the relays 140 and 1.60,which will then continue operated by locking current from the negativebattery 110 over circuits corresponding with those already traced. Forthe fifth impulse current from the negative bus conductor 106 maytraverse the normal contacts of the relay 15 and the forward contacts ofthe rela 25 to energize the segments 75 and 56. n entering the zone E,the brush 127 will accordingly impart a negative impulse to the cable L,while the brush 126 will cause the relay 112 to assume its positivebias, thereby releasing theation of the five impulses already describedas having been prepared in the second channel will now be taken up. Forthe first impulse in this channel current from the positively poled busconductor 109 traverses the normal contacts of the relay 16 and the for-Ward contacts of the relay 26, to the seg- .ments 76 and 57. Arrival ofthe brushes in zone F will accordingly'impart a positive impulse on thecable lead L, establish negative bias of the relay 112 to release therelays 34, 140 and 160 and operate and lock the relays 35, 140 and 160.Since the second impulse in this channel is also of positive polarityand on the basis that the receiving devices at a distant sta'tion (notshown) may be of such type that so-called block signals may be receivedit will new result that, in substitution of the second positive impulsethe cable will be grounded during this interval. For this grounding, atthe moment the brushes arrive in the zone G a circuit may be traced fromthe cable segment 87, brush 127,'segment 77 and the right-hand normalcontacts of the relay 27 to a grounded bus conductor 121. At this timethe brush 126 establishes the positively energized segment 57 to effectpositivebias of the relay 112 to separate its contacts 113, therebydisconnecting the relays 35, 140 and 160, while operating the relay 36and locking it and also'the relays 140 and 160 over the contacts 114 ofthe relay 112. Since the third impulse is also of positive polarity, thecable will again be grounded in substitution of such current and thisgrounding may be traced from the cable segment 88 by way of the brush127 on its arrival in the zone H, segment 78 and the right-hand normalcontacts of the relay 28 to the grounded bus conductor 121.Corresponding with this interval, although the brush 126, may be overthe segments 48, 58 and 67, no circuit 7 changes result since thesegments 5877 are trol relay 112 and relays 36, 140 and 160 continueoperated as previously established by v the passing of the brush 126through the zone G. The fourth impulse of the present selection beingofnegative polarity a connection may be traced from the negative busconductor 106 by way of. the forward contacts of the relays 19 and 29respectively to'the segments 79 and 60. Therefore, on arriving in thezone I the brush 127 establishes this negative current with the cablelead L, while the brush 126 in this zone is ineffective since thesegment 59 stands connected to earth over the right-hand contacts of therelay )8 as traced. Referring to the relay 116, the fourth or negativeimpulse will cause this relay to assume its bias to close its contacts118, thereby establishing a circuit to modify or reduce the potential ofthe negative currentwhich may be effective with the line conductor Lduring this fourth impulse interval. This potential reducing circuit maybe traced from the negative bus .conductor 106, contacts 118 of therelay 116,

resistance unit 167, contacts 162 of the relay 160, thence by way of theleft-hand normal contacts of the relay 27 and the lefthand forwardcontacts of the relay 36 to earth. in parallel with the resistance 16?,

a second circuit may be traced through the resistance 168, the contacts163 of the relay 160, and the left-hand normal contacts of re lays 28and 37 respectively. Therefore, it

will be clear that during the time the brush 127 may be efiective inapplying the fourth or negatively poled impulse to the cable L theresistances 167 and 168 will stand connected from the bus conductor 106to earth, and

due to the presence of the resistance 105 in the path from the battery104 through which this bus conductor is energized a correspondingreduction in the potential of this negative current will result withrespect to the cable lead 11. During the time the resistances 167 and168 are in circuit as described, the other resistances 1 16-150, 166 and169 and 170 are ineffective due to their respective circuits standingopen at the normal contacts of the relays 2125 and 29, the contacts ofthe latter relay serving at this time to disable both of the resistances169-170. The last or fifth impulse in the present selecting combinationbeing of positive polarity, current therefor may be traced from thepositive bus 109, normal contacts of the relay 20, forward contacts ofthe relay 30, thence from the segment by way of the brush 127 and thesegment to the cable L. During this interval the brush 126 having alsoarrived in zone J, it establishes the negatively charged segment 60 tobias the relay 112 to separate its contacts 113, thereby releasing therelays 36, 140 and 160; at this time the brush 136 also causesenergization of the relays 39, 140 and 160 which will then continuelocked through the contacts 11% of relay 112. The last describedoperation completes the sendingof the five character selecting impulsesfor the second channel and the circuits prepared by the operation of therelays 39, 140 and 160 may or may not become effective depending onwhether following impulse intervals may require grounding of the cableas already described.

In briefly describing the circuit conditions whereby various differentcombinations of the potential limiting resistance units may be appliedto transmitted impulses, a number of examples will now be assumed anddescribed.

For a combination in which grounding of the cable takes place onlyduring an interval corresponding with a single impulse, let it beassumed that a permutation of impulses corresponding with alternatepolarities, as already described, are prepared for the first channel,while a similar combination of impulses,'beginnin with a negativeimpulse is prepared in the second quadrant or channel.Accordingly,transmitter levers 2, 1, 6, 8 and 10 will stand operatedwhile relays 12, 14, 16, 18, 20 and'relays 22-25 and 27- 30 will alsostand operated. Since, for such combinations, the fifth impulse of thefirst channel would be of negative polarity the same as the firstimpulse in the second channel, the cable will be grounded during thetime the brush 127 is in the first zone F of the latter channel.Therefore, on the brushes arriving in the zone G, the relays 35, 1&0 and160 will be standing locked as operated due to the brush 126 in passingthrough the zone F; accordingly, a circuit may be traced from thepositivebus conductor 109, contacts 117 of the relay 116, the resistanceunit 166, contacts 161 of the relay 160, the normal, contacts of therelay 26, a conductor 122 to earth, over the left-hand forward contactsof the relay 35. At this time the other resistances associated with therelays M0 and 160 are rendered ineffective through the separatedcondition of the left-hand normal contacts of the relays 2225 and 2730.

For a condition in which the cable may have been grounded during aperiod of three successive impulse intervals, equipment in the firstchannel may be considered as positioned, as already described, for thetransmission of alternate positive and negative impulses beginning witha negative impulse, while the equipment of the second channel will bepositioned to transmit three negative impulses followed by a fourthpositive impulse and' a fifth impulse of negative polarity. Accordingly,the transmitter levers 2, 1, 6, 7, 8, 10 and relays 12, 14, 1618, 20,2225 and 29 and 30 will stand operated while the remaining equipmentwill be positioned as shown in the drawing. On the brush 126 arriving inthe zone 13, the resistance control relays 35, 1 10 and 160 will beoperated and continue in that condition until the brushes arrive in thezone 1 when an impulse of positive current will be imparted to thecable. At such instant, a circuit may be traced from the positive busconductor 109 by way of the contacts 117 of the relay 116, thence by wayof the resistances 166, 167 and 168 to earth at the forward contacts ofthe relay 35, the circuits for these resistances being respectivelycompleted over the contacts 161, 162 and 163 of relay 160 and theleft-hand normal contacts of the relays 26, 27 and 28, by way ofconductor 122. At this time all other resistances will standdisconnected at the separated left-hand contacts of the relays 22-25 and29 and 30.

Assuming now that while the set-up, al-

' ready described, is present for the first channel, a combinationcomprising four negative impulses followed by a positive impulse isprepared for the second channel. Accordingly, the transmitter levers 2,4, 69 and which it is shown. On the brush 126 arrivrelays 12, 14,'16-l9and 2125 and 3'0'will stand operated, while the remainder of theequipment will continue in the position in ing in the zone-F, relays 35,140 and 160 will be operated and held locked until the brushes arrive inthe zone J During the time the brush 127 establishes these preparedpositive impulses with the cable L, four resistance units, 166-469,- arerendered'effective through the contacts 117 of the relay 116 from thepositive control bus conductor 109. These circuits may be further tracedover the left-hand normal contacts of the relays 26-29 and theconductor" 122 to earth, over the forward'contacts of the relay 35. Thecircuit path of the resistance 169, in addition to extending throughthe'contacts of the relays 26, 27 and 28, also includes the normalcontacts of the relays 36, 37 and 38, while, in a corresponding manner,the circuit of the resistanee'168 extends through the normal contacts ofthe relays 36 and 37, and the circuit of the resistance 167 extendsthrough the contacts of the relay 36.

Without considering other intermediate steps or possible variations incurrent po-- tentials, an example will now be assumed wherebymodification of an impulse may I take place following an'intervalcorresponding 'with eight successive impulses during which the cable mayhave been'grounded;

. ergized until the brushes have passed en'- tirely out of the secondchannel section and have passed through the first three impulse zones A,B and Got the first section and arrived at the'fourthzone D to establishthe prepared positive impulse with the cableconductor. At this time theresistances 146, 147, 148, 166, 167, 168,- 169 and 170 will standconnected through the contacts 117 of the relay 116 from the positivebus conductor 109 to earth over the forward contacts of the relay 35.The path for the resistance 148 may be traced through the contacts 143of the relay 140, thence over the left-hand normal contacts of therelays 23, 32, 22, 31 and 21 to continue over a conductor 123 and thelefthand normal contacts of the relays 40, 30, 39, 29, 38, 28, 37, 27,36 and 26 and the conductor 122 to ground at the contacts of the relay35. The routing-of the circuit just traced for the resistance 148represents the longest path-and it will be noted that the respectivecircuits of the other resistances may be traced as'extending in jointrelationover portions of this circuit.

'From the foregoing examples, it will be clear that the number ofresistances which may be applied in reducing the potential of either oneof the line batteries may correspond with the number (if successiveimpuse intervals during which the cable may have continued grounded, andin this man ner it has been found that such inverse polarity reductionof a line battery with respect to the duration of a "cable groundingperiod permits a relatively true zero current condition to be maintainedin 'a line conductor'having, high electrostatic capacity.

It will be understood that the capacity of the multiplex equipment maybe either quadruplex, sextuplex or in accordance with any other of thewell-known service capacity arrangements, or the equipment may have thecapacity of only a single channel coresponding with the equipment shownin Fig. 2 of the drawing. Therefore, when the brushes 126 and 127-leavethe zone J they may proceed through other similar quadrants or channelsections and' at a proper time arrive at and again traversethedistributer sections of the Figs. 1 and 2 inainanner similar to thatalready describcd. In' case the multiplex equipment comprises} only asingle channel, as the channel equipment in Fig. 2, the brushes 126 and127 after leaving the last impulse zone J may immediately reenter thefirst impulse zone F to again traverse the equipment of this channel.

In order that suitable reversals of current polarities may always bepresent with the cable conductor L 'as commonly required forsynchronizing purposes,- etc, as Well understood in the art, busconductors 102 and 103 of the battery 101 stand transposed with respectto the transmitting contacts 15 ofthe first channel and the transmittingcontact 6-10 of the second channel, while in corresponding manner theline battery bus conductors 106 and 109 also stand transposed withrespect to the control contacts of the pole changer relays 11-15 ofthefirst channel and the pole changer relays 16-20 of the second channel.By this arrangement it will be clear that during such times as theequipments of both channels may be idle, thepole changer relays 21 and.26 of the respective channels will stand normally operated. The operating circuit for the relay 21 may be-traceil from the negative busconductor 102 over the transmitter lever 1, winding of relay 21, theconductor 120, thence through the transmitter contact lever 10 to thepositively poled bus conductor 103, and'in corresponding manner theenergizing circuit for the relay 26 may be traced from the negative busconductor 102 by Way of the transmitter lever 5, a conductor 119, thewinding of the relay 26, and the transmitter lever 6 to the positivelypoled bus conductor 103. Although the transmitters of the respectivechannels may be idle, the distributer equipment may continue to operateand each time the brushes pass through the first impulse zone A of thefirst channel, an impulse of negative current will be applied to thecable L, while each time the brushes pass through the first impulse zoneF of the second channel, an impulse of positive current will be appliedto the cable L. During such idle running the potential of these impulseswill be reduced in a manner similar to that already described inconnection with other impulses. This will be clear since grounding ofthe cable will be effected during the time the brushes are traversingthe impulse Zones 13-13 and GJ. To make this clear an inspection of thedrawing will reveal that when the brushes have returned to retraversethe impulse zone A the relays 36, 140 and 160 will be locked in theiroperated positions, thereby permitting a circuit to be traced from thenegative bus conductor 106,

. contacts 118 of relay 116, thence branching jointly through theresistances 167170, the longest circuit for which may be traced throughcontacts 165 of the relay 160 and through the left-hand normal contactsof the relays 30, 39, 29, 38, 28, 37, 27, thence to earth over theleft-hand forward contacts of the relay 36. The other resistances146-150 and 166 at this time stand disconnected at the left-hand normalcontacts of the relays 21 and 26 respectively. At an instant the brushesmay arrive in the impulse zone F of the second channel, the relays 31,140 and 160 will be held locked in an energized condition, therebypermitting a circuit to be traced from; the positive bus conductor 109by way of the contacts 117 of the polar relay 116 to complete branchcircuits through the four resistance units 147-150, the longest circuitfor these units may be traced from the contacts 145 of the relay 140,thence by way of the left-hand normal contacts of the relays 25, 34, 24,33, 23, 32 and 22, thence over the left-hand forward contacts of therelay 31 to earth. At this time the resistance unit 146 stands open atthe left-hand normal contacts of the relay 21, while the resistanceunits 166-170 stand open at the left-hand normal contacts of the relay26. From the circuits just traced it will be clear that the impulsesdescribed will be reduced in strength four-fold and since this reductionis uniform for both the positive and negative impulses it resultslevers, while a corresponding transposition should be made with respectto the negative and positive line battery bus conductors 106 and 109 asrelates to the contact stops of the corresponding pole changer relay.Such transpositions would in turn necessitate that at a distantreceiving station (not shown) the corresponding receiving devices beconnected in such relation to their local operating circuits that theymay properly respond to an operated position of the cor: respondingtransmitter contacts and pole changer relay at the present station undersuch transposed relation of the bus conductors. Positive and negativeimpulses would therefore be transmitted to the line L for each trip ofthe distributer brushes during periods that the transmitting equipmentmay be idle.

What is claimed is:

1. The method of telegraphic transmission which consists in grounding aline conductor in substitution of consecutive impulses oflike polarityand in varying the strength of telegraphic impulses in accordance with apredetermined scale of electrical characteristics controlled bytheduration of the preceding grounded interval.

2.. Themethod of telegraphic transmission which consists in grounding aline conductor in substitution of successive repetitions of impulses oflike polarity and in varying the strength of an impulse whichmay followsuch grounding.

3. The method of telegraphy which con sists in grounding a line insubstitution of successively recurring impulses of like polarity and inreducing the potential of the next impulse of opposite polarity to somelower value dependent upon the length of time such grounding intervalmay have continued.

4. In a telegraph system, means for the tranu lission of characterselecting im ulse combinations formed of permutations o currentpolarities, means for employing intervals ofno current to correspondwith periods during which successive impulses of like polarity would 'berepeated, and means for varying the potential of an impulse which mayfollow such interval of no current.

5. In a telegraph system, a line conductor, means for applying impulsesof dill'erent polarity 1n signaling over said line, means tion ofperiods corresponding with successive repetitions of impulsesof likepolarity,

and means for reducin the potential of an impulse which may follow agrounding period.

6. In a telegraph system, a line conductor, means for employing currentsof opposite polarities in signaling over said line, drainage means forpreventing excess charging of said conductor by current of eitherpolarity, and means for modifying the potential of an impulse nextfollowing the application of such drainage means to said line conductor.

7. In a telegraph system, a line conductor, means foremployingpermutations of current impulses of opposite polarities in signalingover said line, means for'grounding said line in substitution ofsuccessive repetitions of impulses of like polarity, and means forrendering the potential of a next impulse of opposite polarity inverselyproportional to the length of time such grounding interval may have beenefi'ective. I

8. In a telegraph system, a line conductor, duplex equipment therefor,sources of current, pole changer means for applying impulses of eitherpolarity from said sources of current to said line conductor, switchingmeans for normally grounding said line conductor, mea-n controlled bysaid switching means for extending current polarities selected bysaidpole changers, means controlled by said distributer forapplying saidextended polarities to said line conductor, potential modifying meansfor varying the strength of currents supplied to said line, and meanscontrolled by the operation of said distributer for rendering saidpotential modifying means effective to vary the potential of thecurrents supplied to said line conductor. 7

9. In a system of multiplex telegraphy, a

line conductor, distributer means therefor, 7

means for controlling impulses of opposite polarlty in signaling oversaid line, means for normally groundlng said line conductor,

means for Varying the P tential of said im- '3 pulses, meanscontrolledin the operation of said distributor for rendering said potentialvarying means effective to modify the potential of an impulse which mayfollow an interval during which said grounding means may have beeneffective with said line conductor.

10. In a telegraph system, a line conductor, means for applying currentsof predetermined potentials and opposite polarities in signaling oversaid line, means controlled in the transmission of said impulses toground said line conductor in substitution of successive impulseintervals of like polarity, and mean controlled in said groundingoperations to prepare circuits for diminishing the potential of animpulse to a predetermined degree depending on the number of impulseintervals during which the line conductor may have been groundedpreceding the transmission of such diminished impulse.

11. In a telegraph system, sources of current, a line conductor,transmitter contacts for preparing predetermined permutations ofpolarities from said currents, pole changer relays controlled by saidtransmitter contacts, current potential modifying relays controlled bysaid transmitter contacts, distributer means to cooperate with said polechanger relays and said potential modifying relays for applying saidselected polarities to said line conductor, a third plurality of relayscontrolled by said distributer, a plurality of master relays controlledjointly with said third plurality of relays, a polar relay controlled bysaid distributer for establishing locking of said third plurality ofrelays and said master relays, resistance units jointly controlled bysaid master relays and said third relays, a second polar relaycontrolled by current polarities applied to said line, conducter, andmeans controlled by said second polar relay to serve jointlywith saidmaster rclays and said potential controlling relays to render saidresistances efi'ectivc'to vary the potential of an impulse of eitherpolarity which may be applied to said line conductor.

5:1 In witness whereof I hereunto subscribe "my name this 6th day ofAugust, A. D.

JOHN H. BELL.

